US2002159913A1PendingUtilityA1

Sn-Ag-Cu solder and surface treatment and parts mounting methods using the same

37
Priority: Sep 29, 1999Filed: Apr 23, 2002Published: Oct 31, 2002
Est. expirySep 29, 2019(expired)· nominal 20-yr term from priority
Inventors:Toshihide ItoShiro Hara
B23K 35/262C22C 13/00
37
PatentIndex Score
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Cited by
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References
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Claims

Abstract

A Pb-free solder is provided, which has a satisfactory low melting point and suppresses effectively the “copper leaching” phenomenon. The solder is difficult to be oxidized and has a high wettability. The solder consists essentially of (a) 1.0 to 4.0 wt % of Ag, (b) 0.4 to 1.3 wt % of Cu; (c) at least one of 0.02 to 0.06 wt % (or 0.02 to 0.04 wt %) of Ni and 0.02 to 0.06 wt % (or 0.02 to 0.05 wt %) of Fe; and (d) a balance of Sn. The solder has a copper dissolution rate of 0.20 or 0.15 μm or less. Preferably, the solder has a liquidus temperature of 240° C. or lower, in which a satisfactory low melting point is ensured. More preferably, the solder has a liquidus temperature of 230° C. or lower. It is preferred that the solder has a viscosity of 2.5 cP or lower.

Claims

exact text as granted — not AI-modified
What is claimed is:  
     
         1 . A lead-free solder consisting essentially of: 
 (a) 1.0 to 4.0 wt % of Ag;    (b) 0.4 to 1.3 wt % of Cu;    (c) 0.02 to 0.06 wt % of Ni; and    (d) a balance of Sn;    wherein said Ni serves to lower a copper dissolution rate of said solder.    
     
     
         2 . The solder according to  claim 1 , wherein a content of Ni is in a range from 0.02 to 0.04 wt %.  
     
     
         3 . The solder according to  claim 1 , wherein said solder having a copper dissolution rate of 0.20 μm or less.  
     
     
         4 . The solder according to  claim 1 , wherein said solder having a liquidus temperature of 240° C. or lower.  
     
     
         5 . The solder according to  claim 1 , wherein said solder having a liquidus temperature of 230° C. or lower.  
     
     
         6 . The solder according to  claim 1 , wherein said solder has a viscosity of 2.5 cP or lower.  
     
     
         7 . The solder according to  claim 1 , further containing 0.02 to 0.06 wt % of Fe.  
     
     
         8 . The solder according to  claim 1 , further containing 0.02 to 0.05 wt % of Fe.  
     
     
         9 . A lead-free solder consisting essentially of: 
 (a) 1.0 to 4.0 wt % of Ag;    (b) 0.4 to 1.3 wt % of Cu;    (c) 0.02 to 0.06 wt % of Fe; and    (d) a balance of Sn;    wherein said Fe serves to lower a copper dissolution rate of said solder.    
     
     
         10 . The solder according to  claim 9 , wherein a content of Fe is in a range from 0.02 to 0.05 wt %.  
     
     
         11 . The solder according to  claim 9 , wherein said solder having a copper dissolution rate of 0.20 μm or less.  
     
     
         12 . The solder according to  claim 9 , wherein said solder having a liquidus temperature of 240° C. or lower.  
     
     
         13 . The solder according to  claim 9 , wherein said solder having a liquidus temperature of 230° C. or lower.  
     
     
         14 . The solder according to  claim 9 , wherein said solder has a viscosity of 2.5 cP or lower.  
     
     
         15 . A method of surface-treating a PWD, comprising the steps of: 
 (a) preparing said solder according to  claim 1;  and    (b) selectively coating said solder on a Cu circuit layer of a PWB.    
     
     
         16 . A method of surface-treating a PWD, comprising the steps of: 
 (a) preparing said solder according to claim  7 ; and    (b) selectively coating said solder on a Cu circuit layer of a PWB.    
     
     
         17 . A method of surface-treating a PWD, comprising the steps of: 
 (a) preparing said solder according to claim  9 ; and    (b) selectively coating said solder on a Cu circuit layer of a PWB.    
     
     
         18 . A method of mounting electronic parts on a PWD comprising the steps of: 
 (a) preparing said solder according to  claim 1;  and    (b) soldering electronic parts on a Cu circuit layer of a PWB with said solder.    
     
     
         19 . A method of mounting electronic parts on a PWD comprising the steps of: 
 (a) preparing said solder according to claim  7 ; and    (b) soldering electronic parts on a Cu circuit layer of a PWB with said solder.    
     
     
         20 . A method of mounting electronic parts on a PWD comprising the steps of: 
 (a) preparing said solder according to claim  9 ; and    (b) soldering electronic parts on a Cu circuit layer of a PWB with said solder.

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